# coding: utf8
from Tkinter import *
import tkFont
from functools import partial


def get_input(entry, argu):
    entry.insert(END, argu)

def backspace(entry):
    print (entry.get())
    input_len = len(entry.get())
    entry.delete(input_len - 1)  
  
def clear(entry):  
    entry.delete(0, END)  
  
def calc(entry):  
    input = entry.get()  
    output = str(eval(input.strip()))  
    clear(entry)  
    entry.insert(END, output)  

def cal():
    root = Tk()
    root.title("Python 计算器")
    # root.resizable(0,0)

    # 输入框初始化
    entry_font = tkFont.Font(size=12)
    entry = Entry(root, justify="right", font=entry_font)
    entry.grid(row=0, column=0, columnspan=4, sticky=N+W+S+E, padx=5, pady=5) 

    # 按钮初始化
    button_font = tkFont.Font(size=10, weight=tkFont.BOLD)
    button_bg = '#D5E0EE'
    button_active_bg = '#E5E35B'
    myButton = partial(Button, root, bg=button_bg, padx=10, pady=3, activebackground=button_active_bg)

    # 初始化按钮 7
    button7 = myButton(text='7', command=lambda : get_input(entry, '7'))
    button7.grid(row=1, column=0, pady=5)

    # 初始化按钮 8
    button8 = myButton(text='8', command=lambda : get_input(entry, '8'))
    button8.grid(row=1, column=1, pady=5)

    # 初始化按钮 9
    button9 = myButton(text='9', command=lambda : get_input(entry, '9'))  
    button9.grid(row=1, column=2, pady=5)  

    # 初始化按钮 +
    button10 = myButton(text='+', command=lambda : get_input(entry, '+'))  
    button10.grid(row=1, column=3, pady=5)  

    # 初始化按钮 4
    button4 = myButton(text='4', command=lambda : get_input(entry, '4'))  
    button4.grid(row=2, column=0, pady=5)  

    # 初始化按钮 5
    button5 = myButton(text='5', command=lambda : get_input(entry, '5'))  
    button5.grid(row=2, column=1, pady=5)  

    # 初始化按钮 6
    button6 = myButton(text='6', command=lambda : get_input(entry, '6'))  
    button6.grid(row=2, column=2, pady=5)  

    # 初始化按钮 -
    button11 = myButton(text='-', command=lambda : get_input(entry, '-'))  
    button11.grid(row=2, column=3, pady=5)  

    # 初始化按钮 1
    button1 = myButton(text='1', command=lambda : get_input(entry, '1'))  
    button1.grid(row=3, column=0, pady=5)  

    # 初始化按钮 2
    button2 = myButton(text='2', command=lambda : get_input(entry, '2'))  
    button2.grid(row=3, column=1, pady=5)  

    # 初始化按钮 3
    button3 = myButton(text='3', command=lambda : get_input(entry, '3'))  
    button3.grid(row=3, column=2, pady=5)  

    # 初始化按钮 *
    button12 = myButton(text='*', command=lambda : get_input(entry, '*'))  
    button12.grid(row=3, column=3, pady=5)

    # 初始化按钮 0
    button0 = myButton(text='0', command=lambda : get_input(entry, '0'))  
    button0.grid(row=4, column=0, columnspan=2, padx=3, pady=5, sticky=N+S+E+W)  

    # 初始化按钮 .
    button13 = myButton(text='.', command=lambda : get_input(entry, '.'))  
    button13.grid(row=4, column=2, pady=5)  

    # 初始化按钮 /
    button14 = Button(root, text='/', bg=button_bg, padx=10, pady=3,  
                    command=lambda : get_input(entry, '/'))  
    button14.grid(row=4, column=3, pady=5)  

    # 初始化按钮 <-
    button15 = Button(root, text='<-', bg=button_bg, padx=10, pady=3,  
                    command=lambda : backspace(entry), activebackground = button_active_bg)  
    button15.grid(row=5, column=0, pady=5)  

    # 初始化按钮 C
    button16 = Button(root, text='C', bg=button_bg, padx=10, pady=3,  
                    command=lambda : clear(entry), activebackground = button_active_bg)  
    button16.grid(row=5, column=1, pady=5)  

    # 初始化按钮 =
    button17 = Button(root, text='=', bg=button_bg, padx=10, pady=3,  
                    command=lambda : calc(entry), activebackground = button_active_bg)  
    button17.grid(row=5, column=2, columnspan=2, padx=3, pady=5, sticky=N+S+E+W)

    root.mainloop()


if __name__ == '__main__':
    cal()